There is a concern with the carbon stored in the form of frozen partially decomposed vegetation in the vast tundra of the north. When the permafrost melts, it may releases carbon in the form of carbon dioxide and methane, both of which are greenhouse gases. The amount of greenhouse gases which will be released from the Arctic’s stockpile of carbon may be more secure than scientists thought. In a 20-year experiment that warmed patches of chilly ground, tundra soil kept its stored carbon, researchers report. Almost half of the world’s soil carbon is stored at high latitude, in the form of dead and decaying organisms.

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Arctic methane release is the release of methane from seas and soils in permafrost regions of the Arctic. While a long-term natural process, it may be exacerbated by global warming. This results in a positive feedback effect, as methane is itself a powerful greenhouse gas.

The Arctic region is one of the many natural sources of the greenhouse gas methane. Global warming accelerates its release, due to both release of methane from existing stores, and from methanogenesis in rotting biomass. Large quantities of methane are stored in the Arctic in natural gas deposits, permafrost, and as submarine clathrates. Permafrost and clathrates degrade on warming, thus large releases of methane from these sources may arise as a result of global warming.

In 1989, ecologists set up greenhouses on plots of tundra in northern Alaska. Air temperature inside the greenhouses was on average 2 degrees Celsius warmer than outside.

The results of a two-decade summer warming experiment in an Alaskan tundra ecosystem were reported by researchers at the University of California. The team reports, mosses and lichens gave way to woody shrubs. Decomposition slowed in surface soil while it sped up deeper underground. Warmer soils may have allowed plant roots and plant litter to penetrate farther into the ground, increasing both the deep soil’s carbon stocks and its rates of decomposition, the researchers suggest.

Overall, though, there was no difference in total soil carbon in the greenhouse plots compared with plots that had no greenhouses.